CVE-2019-13126 in NATS Server
Summary
by MITRE
An integer overflow in NATS Server before 2.0.2 allows a remote attacker to crash the server by sending a crafted request. If authentication is enabled, then the remote attacker must have first authenticated.
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Analysis
by VulDB Data Team • 03/30/2026
The vulnerability CVE-2019-13126 represents a critical integer overflow flaw in the NATS messaging server software that existed prior to version 2.0.2. This vulnerability specifically affects the network address translation functionality within the NATS server implementation, creating a condition where a remote attacker can deliberately manipulate input data to cause the server to crash. The flaw manifests when the server processes certain network requests that involve integer calculations, where the arithmetic operations exceed the maximum representable value for the integer data type, leading to unexpected behavior and system instability.
The technical exploitation of this vulnerability requires a specific sequence of conditions to be met. While the flaw exists in the NATS server's handling of network traffic, it does not allow for arbitrary code execution or direct access to system resources. Instead, the integer overflow occurs during the processing of network packets that contain crafted data values designed to trigger the overflow condition. When the server attempts to perform calculations with these malformed values, the integer overflow causes the application to behave unpredictably and ultimately results in a crash. This type of vulnerability falls under the CWE-190 category of integer overflow, which is a well-documented class of software flaws that can lead to system instability and denial of service conditions.
The operational impact of this vulnerability extends beyond simple server crashes, as it can be leveraged to create sustained denial of service attacks against NATS server deployments. Organizations relying on NATS for mission-critical messaging infrastructure face significant risk from this flaw, particularly in environments where continuous availability is essential. The vulnerability affects all NATS server installations running versions prior to 2.0.2, making it a widespread concern across various deployment scenarios including cloud environments, containerized applications, and traditional server deployments. Attackers exploiting this vulnerability can cause service disruption without requiring elevated privileges beyond authentication, making the attack surface broader than many other server-side vulnerabilities.
The mitigation strategy for CVE-2019-13126 primarily involves upgrading the NATS server software to version 2.0.2 or later, which includes patches specifically designed to address the integer overflow condition. Organizations should prioritize this upgrade as a critical security measure, particularly in production environments where NATS server availability is paramount. Additionally, network administrators should implement monitoring solutions to detect anomalous traffic patterns that might indicate attempted exploitation of this vulnerability. Security teams should also consider implementing access controls and authentication mechanisms to limit exposure, as the vulnerability requires successful authentication to exploit when authentication is enabled. From an ATT&CK framework perspective, this vulnerability aligns with the T1499.004 technique of network denial of service, where adversaries leverage software flaws to disrupt network services and maintain system availability. Organizations should also review their incident response procedures to ensure readiness for potential exploitation attempts, as the crash condition can be difficult to distinguish from other network failures without proper monitoring and logging capabilities in place.